1. Field of the Invention
The invention relates to a gas laser with high-frequency excitation, having at least one laser tube, to which at least one pair of electrodes for the high-frequency excitation is externally fitted, and having at least one inlet connection and one outlet connection for the gas.
2. Background and Description of the Prior Art
In such gas lasers, a gas or plasma which is excited by the high frequency flows through the laser tube. In this procedure, the high-frequency excitation displaces the gas into such a condition that laser action can take place between appropriate mirrors. In this procedure, the gas is very intensely heated by the high-frequency excitation, so that it must be cooled; this takes place by means of an appropriate circuit, in which the gas is also conducted past a heat exchanger.
Metal blocks are disposed at the positions at which the gas is supplied and withdrawn, in which blocks there is inserted the actual laser tube, which in most cases consists of quartz glass. The objective is to make the distance between the pairs of electrodes and these blocks as small as possible, so that compact external dimensions are imparted to the laser. Moreover, in this instance, at least in the case of the outlet connection, this arrangement achieves the advantage that the hot gas path between electrodes and the outlet connection becomes as small as possible. This is essential, since the hot gas or plasma is no longer excited by the high frequency in this region, but, because of its high temperature, no longer leads to optimal laser activity. If the temperature in this region is very high, i.e. higher than approximately 500 degrees K then it is even possible here for absorption of the laser power to take place.
If, however, as is desirable per se for the two reasons which have been mentioned, the distances between the electrodes and the outlet blocks, which normally consist of metal, are now made very small, parasitic discharges take place via the gas or plasma between the electrodes and the block. However, in all circumstances it would be desired that these parasitic discharges, which are difficult to control, should be avoided. It was formerly only known to increase the distance between pairs of electrodes or outlet blocks; however, this leads to the abovementioned disadvantage of the longer hot gas path. On the other hand, if the outlet blocks are produced from ceramic or similar material, the entire installation becomes very expensive.
3. Objectives of the Invention
It is an objective of the invention to make smaller the distance between the pairs of electrodes and the outlet connection in such a gas laser, without the system becoming more expensive as a result or parasitic discharges being caused, thereby minimizing undesired absorbtion of laser energy.